This invention relates to a cathode ray tube device which comprises a cathode ray tube held in an electromagnetic shielding casing by means of an elastic body.
Hitherto, a cathode ray tube has been widely used with a control device of mechanical or other apparatuses as means for transmitting instructions or information. Some of these mechanical or other apparatuses are sometimes applied in a very rigid environment or demanded to have a high reliability. For instance, a cathode ray tube may be cited which is used with a control system of airplanes or automobiles. With a cathode ray tube device used for such object, a cathode ray tube is held by an elastic body prepared from, for example, silicone resin in an electromagnetic shielding casing. The purpose is to let the cathode ray tube device withstand changes in a magnetic field resulting from variations in a magnetic field prevailing in a near-by implement or geomagnetism or resist mechanical vibrations. FIG. 1 schematically illustrates this arrangement. A cathode ray tube 1 is held in an electromagnetic shielding case 2 (hereinafter referred to as "a case") by an elastic body 3. This arrangement enables the cathode ray tube 1 to be shielded by the case 2 from variations in an external magnetic field prevailing in the environment in which said cathode ray tube 1 is applied, and also protected from mechanical vibrations by means of said elastic body 3. However, the conventional cathode ray tube device of FIG. 1 has the drawbacks that when the environment in which said cathode ray tube device is applied is considerably heated, then the elastic body 3 is thermally expanded, causing a thermal stress to be applied to the funnel section of the cathode ray tube in a direction indicated by arrows A and eventually causing the cathode raytube 1 to be axially pushed out of the case 2 in a direction indicated by an arrow B. To reduce the extent to which the cathode ray tube 1 is pushed, it may be advised to reduce the degree in which the funnel section of the cathode ray tube 1 is inclined to the axial direction thereof. However, the extent to which the funnel section of the cathode ray tube 1 can be inclined is extremely limited from the standpoint of manufacturing a glass bulb. In start, an attempt to carry out the above-mentioned modifications is practically impossible.